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Create your own charging timer

Create your own charging timer

Submitted by mark_g on 21. Januar 2013

If you have time of use (TOU) billing for you utility bill, I have found a simple approach to approximate a charging timer. Generally, I will start charging at 7PM but my off-peak does not start until 12AM which means most of my charging is complete by then. Until Tesla comes out with a charging timer option and I do not want to make a special trip to the garage at midnite to take advantage of the (much) lower off peak rates, I simply set the max amp setting to whatever is needed to stretch out the charging time until 6AM. For example, an amp setting of 10A , will take about 10 hours to charge instead of the 2.5 at 40A which means that now most of my charging is done in the off peak period. Although not perfect, I have reduced my electric bill by half over what it otherwise would be.

shop |
21. Januar 2013

Great idea! It may even be marginally better for the battery pack too.

Brian H |
21. Januar 2013

You also get the benefit of warm battery and full power and regen in the morning (if you're in a cold climate where that's a concern).

drp |
21. Januar 2013

It seems to me that one of the easiest things to do is to program a time charge in the computer system. I expect that one will be able to program the car to finish the charging 15 minutes before they want to leave. The car should know how much juice it needs based on the draw and therefore can shut the car off the charging system until the required time it needs to begin in order to finish before leaving in the morning. For example, If you have to leave the house at 6:30 AM, tell the car to be finished charging by 6:15 AM. This would also allow the batteries to stay warm, or cool, depending on the climate, until it is time to go. This also would allow for warming/cooling the interior cabin while charging.

shs |
21. Januar 2013

I would think that one could use a 50 amp 240 volt contactor (big relay) controlled by a 120 volt timer to only charge after midnight as a short term measure. Would there be a problem plugging in a "dead" charging cable and having the charging start when the voltage appeared after midnight?

Brian H |
21. Januar 2013

If you're "timing" it, schedule it to end 15 minutes AFTER you take the car. That way it's sure to be warm, and the "missed" mileage will be negligable. Use the screen to "End Charge".

txjak |
21. Januar 2013

My friend has a Volt and he says he can tell it when he wants it to finish charging and it calculates when to start from there.

DouglasR |
21. Januar 2013

@shs

I would not automatically assume that the car will sense when a dead cable becomes live and simply start charging from that point. It may sense the dead cable as a fault, throw up an error, and not charge again until the cable is removed from the port and re-inserted. Given the amount of intelligence built in to the charging process (and the kind of harm that can be done if the charging goes wrong), the circuit is likely to shut down if there is any question. I would not try this method before speaking to the appropriate Tesla engineers.

shs |
21. Januar 2013

Douglas R,

Thanks, hopefully Tesla will have implemented the in-car charging timer before I have a need to charge.

tezco |
21. Januar 2013

@DouglasR

I suspect the S is set to resume charging in the event of a power glitch or interruption, so the contactor idea would probably work. I think the Blink EVSE has built in timer which controls it's contactor.

Brian H |
21. Januar 2013

shs;
If you do the dead cable experiment, let us know how it goes. Particularly if something explodes. <8-(

f-tal |
21. Januar 2013

I was thinking of putting a contactor on my charging circuit as well, since the plug is located outside. Not that I'm too concerned about unauthorized use, but it may alleviate concerns when connecting during wet weather. I was planning on running the coil voltage through a wall switch (or timer setup I guess) by the side door.

DouglasR |
21. Januar 2013

@tezco

Good point. I would still try to check it out with a Tesla engineer.

Brant |
21. Januar 2013

Thanks for the tip mferr
I have got the same TOU situation
Hadn't thought of that